import java.util.ArrayList;
import java.util.List;

public class Solution1417 {
    public String reformat(String s) {
        List<Character> l1=new ArrayList<>();
        List<Character> l2=new ArrayList<>();
        for (char c : s.toCharArray()) {
            if (c>='a' && c<='z'){
                l1.add(c);
            }else {
                l2.add(c);
            }
        }
        if (Math.abs(l1.size()-l2.size())>1){
            return "";
        }
        StringBuilder stringBuilder=new StringBuilder();
        if (l1.size()>=l2.size()){
            for (int i=0;i<l2.size();i++){
                stringBuilder.append(l1.get(i)).append(l2.get(i));
            }
            if (l1.size()>l2.size()){
                stringBuilder.append(l1.get(l1.size()-1));
            }
        }else {
            for (int i=0;i<l1.size();i++){
                stringBuilder.append(l2.get(i)).append(l1.get(i));
            }
            stringBuilder.append(l2.get(l2.size()-1));
        }
        return stringBuilder.toString();
    }

    public static void main(String[] args) {
        System.out.println(new Solution1417().reformat("covid2019"));
    }
}
